The invention relates to a lens antenna arrangement, preferably for operation; within the microwave range. The arrangement comprises a round disc-shaped lens element, for example a round disc of dielectric plastic material with radially varying refractive index. The lens element has, on at least one of the major sides, a conductive plane and is surrounded by radiators or feeders located at the circumference for reception and transmission of electromagnetic energy passing through the disc-shaped lens element.
Known antennas of this kind are either constructed for a polarization with the E-vector perpendicular to the plane of the lens antenna or a polarization with the E-vector situated in the plane of the lens. If the lens antenna is oriented horizontally the former polarization can be called vertical and the latter horizontal polarization.
It is advantageous if the lens antenna is stationary but nevertheless usable for reception or transmission in different directions by using several feeders situated at different places along the circumference. However, if feeders are arranged along the whole circumference the problem arises, if special measures are not taken, that feeders situated at the opposite half of the circumference relative to a respective feeder may act as attenuators for radiation to or from the respective feeder. In order to avoid this, each feeder must have a small geometrical projection surface as seen in a plane which is perpendicular to the direction of the radiation to or from a respective feeder. Besides the geometrical extension in said plane it is also possible to define an "effective antenna area" for each feeder in said plane which must also be small if the feeders are not to act as strong attenuators. This effective antenna area depends i.a. on the load impedance of the feeder and can be varied by electrical switching operations.
In previously proposed antenna constructions having feeders distributed around the circumference thereof one single feeder is used at a time. Those feeders, which would act as attenuators for the radiation to or from the active feeder are switched electrically so that their effective antenna area is small. This means of course, that these feeders cannot be used either as receiving or transmitting elements as long as they must have a small attenuating effect.